Abstract:

An automatic guided vehicle (10) with an improved multiple-pallet lifting
group comprising a machine body (11) provided with means for its movement
(12) and a lifting group (13) constrained to the machine body (11),
wherein the lifting group (13) comprises a multilevel post structure
(14), a lift truck (15), a tilting plate (17) which constitutes the
framework of a multiple-pallet clamp group (18) provided with three pairs
(19', 19'', 19''') of forks (19) arranged in a specular manner with
respect to a longitudinal centreline plane (22) of the machine body (11)
and moveable along horizontal guides (20) constrained to the framework
(17), the clamp group (18) comprising per each pair (19', 19'', 19''') of
forks (19) two actuators (21) for the independent control of each fork
(19), a pair (24', 24'', 24''') of two oppositely positioned racks (24)
joined integrally to the respective forks (19) and at least one toothed
wheel (23', 23'', 23''') which engages the pair of corresponding racks
(24', 24'', 24''').

Claims:

1. Automatic guided vehicle (10) with an improved multiple-pallet lifting
group comprising a machine body (11) provided with means for its movement
(12) and a lifting group (13) constrained to said machine body (11),
wherein said lifting group (13) comprises a multilevel post structure
(14) provided with a fixed part (31) directly constrained to said machine
body (11) and with a moveable part (32), a lift truck (15) constrained in
a vertically sliding manner to said moveable part (32), a tilting plate
(17), hinged to said lift truck (15), which constitutes the framework of
the clamp group (18), frontally constrained to said plate (17),
characterised in that said clamp group (18) comprises three pairs (19',
19'', 19''') of forks (19), each arranged in a specular manner with
respect to a longitudinal centreline plane (22) of said machine body (11)
and moveable along horizontal guides (20) constrained to said plate (17),
and in that said clamp group (18) comprises per each pair (19', 19'',
19''') of forks (19) two actuators (21) for an independent control of
each of said forks (19), a pair (24', 24'', 24''') of oppositely
positioned racks (24) joined integrally to the respective forks (19) and
at least one toothed wheel (23', 23'', 23''') which engages said
corresponding pair of racks (24', 24'', 24''').

2. Vehicle according to claim 1, characterised in that it comprises a
sensor (25', 25'', 25''') associated to said at least one toothed wheel
(23', 23'', 23''') to detect the position of said pair (19', 19'', 19''')
of forks (19).

3. Vehicle according to claim 1, characterised in that said actuators (21)
are hydraulic actuators constrained at an end to said plate (17) and at
an opposite end to said forks (19).

4. Vehicle according to claim 3, characterised in that both the hydraulic
actuators (21) operating on a pair of said forks (19) are controlled by a
common pump (26, 27).

5. Vehicle according to claim 4, characterised in that a dedicated pump
(26) supplies the actuators (21) of said external pair (19''') of forks
(19) and a shared pump (27) alternatively supplies the actuators of said
pair of internal (19') and intermediate (19'') forks wherein electric
valves (28) positioned on the circuit of each system control the supply
to said systems.

6. Vehicle according to claim 1, characterised in that said forks (19)
comprise seats (41) at their ends for optical sensors (40) for optical
scanning of the space in front of said forks (19).

7. Vehicle according to claim 6, characterised in that said optical
sensors (40) are optical sensors of the photocell type.

8. Vehicle according to claim 1, characterised in that said racks (24) are
directly connected to said forks (19).

9. Vehicle according to claim 3, characterised in that said racks (24) are
connected to said ends of said hydraulic actuators (21) connected to said
forks (19).

10. Vehicle according to claim 2, characterised in that said sensors (25',
25'', 25''') are encoders for measuring the movement of said forks (19).

11. Vehicle according to claim 1, characterised in that said post
structure (14) comprises two parallel vertical hydraulic actuators (30),
in which said fixed part (31) comprises a hydraulic cylinder associated
to a "double T" shaped vertical guide (33) and said moveable part (32),
which is vertically extendable beyond said fixed part (31), is connected
at the upper end to a "double T" shaped vertical guide (33').

12. Vehicle according to claim 11, characterised in that said lift truck
(15) comprises sliding coupling means (34) with respect to said post
structure (14) composed of rotating bearings inside said vertical guides
(33') associated to said moveable part (32).

13. Vehicle according to claim 1, characterised in that said post
structure (14) comprises pulleys (35) and chains (36) constrained at an
end to said lift truck (15) and at the other end to said moveable
portions (32) for transmitting vertical motion of said lift truck (15)
with respect to said post structure (14).

14. Vehicle according to claim 1, characterised in that said post
structure (14) comprises two horizontal-axis hinges (16) which join, at
the upper part, said plate (17) and said lift truck (15) to allow the a
tilting rotation of said plate (17).

Description:

[0001]The present invention regards an automated guided vehicle with an
improved multiple-pallet lifting group. Automatic guided vehicles for
transport of loose, packaged or palletized products inside factories or
warehouses are known. Such automatic guided vehicles are for example of
the wire guided type or of the gyroscope type, adapted to follow preset
guides, or else of the laser-guide type programmable to follow any kind
of path.

[0002]Automatic guided vehicles can be provided with a lifting group for
palletized products and thus serve as a lift truck or as a forklift.

[0003]Lift trucks meet the need to allow quick movement of a large amounts
of products, which, alongside being generally heavy, they are stacked in
special units called "pallets". This movement of products usually occurs
through methods quite common to all current lift trucks.

[0004]In particular, first and foremost, the vehicle is neared to the
pallet intended to be moved. Once reached, the pallet is "seized" at the
lower part by means of forks and eventually lifted and secured integrally
to the lift truck due to particular movements of the forks themselves.
Once reached such configuration the lift truck is free to move and shift
until it reaches the position at which it is to proceed, through steps
opposite to the ones that had characterised seizure and lifting of the
pallet, to laying and positioning of the same pallets.

[0005]According to the above outlined description it is observed that the
forks, which have the function of seizing, lifting, securing to the lift
truck and, subsequently, laying the product, play a crucial role in such
movement procedure of products stacked in pallets.

[0006]The forks, which may vary in terms of numbers and sizes, have an
L-shaped profile whose vertical side extends parallel to the front
section of the lift truck, and can serve as a support base for the
products during transport, while the horizontal one, projecting
longitudinally, allows to seize and support the pallet at the lower part
in a firm manner.

[0007]Usually such forks are free to perform given movements, with respect
to the lift truck, such as a vertical translation movement along some
vertical guides fixed onto the lift truck, and in some cases also
horizontally, along horizontal guides.

[0008]Furthermore, a rotation around a horizontal axis can be allowed, to
incline the products towards the lift truck and, alongside enhancing the
stability of the system, compensate for downward elastic deformation of
the forks caused by the weight of the products themselves. The
abovementioned movements allow to firmly seize and secure the pallet
intended to be moved.

[0009]In order to obtain a good seizure and lifting, the forks are usually
provided in even numbers and, in particular, two adjacent forks engage
the same pallet. Currently, lift trucks with two or three pairs of forks
are also used, in such a manner to allow movement of more products within
a shorter period of time.

[0010]However, current automatic guided vehicles provided with a lifting
group exclusively adopt fixed forks systems for the seizure of pallets of
preset standard sizes and thus do not allow to move different types of
one or more pallets.

[0011]As a matter of fact, only traditional lift trucks manoeuvred by an
operator on board the same lift truck can be provided with
multiple-pallet lifting groups with forks adjustable at various
positions.

[0012]Even traditional lift trucks known today, with their relative
lifting groups, have some drawbacks.

[0013]If the traditional lift truck is provided with a multiple-pallet
clamp, these drawbacks for example may arise from poor accuracy when
positioning the forks or from the failure to be provided with a variable
distance between all the adjacent forks present.

[0014]As a matter of fact, in the common multiple-pallet clamps of
traditional lift trucks in the market, two adjacent forks are part of two
separate pairs wherein usually only one can be freely positioned at a
variable centre distance within a determined range of movement.

[0015]In the presence of a single pump for all the systems, the operation
of a single pair forks, using a flow separator to convey oil only to the
two actuators present, can lead to non-simultaneity of the forks of the
same pair and above all to repeatability errors in their positioning.

[0016]A second drawback regards a non-controllable centre distance between
all the forks and this is due to the fact that in the multiple-pallet
clamps of the traditional lift trucks, only the external forks are
controlled hydraulically while the other forks connected thereto by means
of a device, such as for example a gas spring, which determines its only
two/three possible configurations.

[0017]These drawbacks are such that a traditional multiple-pallet clamp
cannot be used for a lift truck without an operator on board, that is an
automatic guided vehicle, for which accuracy and repeatability of
movements of the forks are key factors.

[0018]Additionally, such traditional equipments, combined with an
automatic guided vehicle, do not guarantee an adequate level of accident
prevention.

[0019]As a matter of fact, falls or erroneous positioning of pallets can
lead to economical losses, such as breakage of products, but they might
also expose the personnel near the lift truck to danger, given that the
material moved is generally very heavy.

[0020]The objective of the present invention is that of providing an
automatic guided vehicle provided with an improved multiple-pallet
lifting group serving as a lift truck provided with a multiple-pallet
clamp capable of overcoming the abovementioned drawbacks.

[0021]Another objective is that of providing an automatic guided vehicle
with an improved multi-pallet lifting group with an ideal synchronisation
of the pairs of forks and with centre distances relatively variable
between all the forks.

[0022]Still another objective is that of being in a position to provide an
automatic guided vehicle with an improved multiple-pallet lifting group
provided with a safety and accident prevention system.

[0023]These objectives according to the present invention are attained by
manufacturing an automatic guided vehicle with an improved
multiple-pallet lifting group as described in claim 1.

[0024]Further characteristics of the invention are described in the
subsequent claims.

[0025]Characteristics and advantages of an automatic guided vehicle with
an improved multiple-pallet lifting group according to the present
invention shall be clearer from the following exemplifying and
non-limiting description with reference to the schematic drawings
attached wherein:

[0026]FIG. 1 is a partially sectioned side view of an automatic guided
vehicle with an improved multiple-pallet lifting group according to the
present invention;

[0027]FIG. 2 is a schematic top-view of the vehicle of FIG. 1;

[0028]FIG. 3 is a schematic cross-section along lines III-III of FIG. 1 of
a detail of the lifting group according to the invention;

[0029]FIG. 4 is a schematic front view of the multi-pallet clamp group of
the vehicle of FIG. 1;

[0030]FIG. 5 is a cross-sectional view of the clamp group according to
line V-V of FIG. 4;

[0031]FIG. 6 shows a simplified hydraulic scheme of distribution of oil to
the systems.

[0032]With reference to the figures, an automatic guided vehicle with an
improved multiple-pallet lifting group is shown and indicated in its
entirety by number 10.

[0033]A schematic example of such a vehicle 10, according to the present
invention is represented, respectively with a side view and a top-view,
in FIGS. 1 and 2.

[0034]Such a vehicle 10, similarly to the devices known and used today,
comprises a machine body 11 provided with means, such as for example a
drive wheel 12, for its movement.

[0035]This vehicle 10 moves horizontally on the plane on which it lies and
it is capable of nearing the products intended to be transferred and
subsequently reach the position at which the same are intended to be
laid. Such movements can be controlled manually by an operator not on
board with a "joystick type" control device, otherwise they can be preset
and subsequently performed in an autonomous manner by the vehicle 10
through communication with a computer referred to as a supervisor.

[0036]Furthermore, vehicle 10, still similarly to the devices known today,
comprises a lifting group 13 constrained, at the rear part, to the
machine body 11.

[0037]This lifting group 13 comprises a vertical multi-level post
structure 14, provided with a fixed part 31 directly constrained to the
body of the machine 11 and with a moveable part. 32, to which a
vertically sliding lift truck 15 is constrained through a system of
pulleys and chains. In addition, the lifting group 13 comprises a tilting
plate 17, hinged to the lift truck 15, which forms the framework of a
clamp group 18, frontally constrained to it.

[0038]The clamp group of the vehicle 10 according to the invention is
provided with three pairs of forks 19, an internal pair 19', an
intermediate pair 19'' and an external pair 19'''.

[0039]Each of these three pairs of forks 19 is arranged in a specular
manner with respect to a longitudinal centreline plane 22 of the machine
body 11. Each fork 19 is moveable horizontally with respect to the
abovementioned plate 17, moving on horizontal guides 20 constrained to
it. According to a preferred embodiment, provided for exemplification
purposes, each fork 19 is provided with a slider 119 with a T-shaped
profile for a sliding coupling within a complementary groove 120 of the
horizontal guides 20.

[0040]According to the invention, as observable in FIGS. 4 and 5, the
horizontal motion of each fork 19 is controlled by a relative actuator
21. Thus, six actuators 21 are used for six forks 19.

[0041]Additionally, according to the invention, each pair of forks 19',
19'' and 19''' comprises a pair of oppositely positioned racks 24', 24''
e 24'''; each rack 24 is joined integrally to its respective fork 19.

[0042]At the centreline plane 22 the plate 17 is provided with at least
one toothed wheel 23', 23'' and 23''' which meshes with the respective
pairs of racks 24', 24'' and 24''', thus attaining the simultaneous
movement of the forks 19 of each pair.

[0043]In FIG. 4, the pairs of racks joined integrally with the central 19'
and intermediate 19'' pairs of forks mesh with the respective pinion 23
and 23'' arranged at the centreline plane 22. The pair of racks 24'''
joined integrally with the external pair of forks 19''' instead meshes
with a gearing, comprising five toothed wheels, among which a central
toothed wheel 23''' at the centreline plane 22.

[0044]A sensor of the encoder type 25', 25'', 25''', is connected on the
pin of each pinion 23' and 23'' and of the central toothed wheel 23''' of
the gearing, as shown in FIG. 5, adapted to measure the movement of the
forks 19 from the relative pair depending on the position of the pair of
racks 24 connected to it. In FIG. 4, on the other hand, the gearing is
shown partially broken away and thus the encoder 25''' connected to the
central toothed wheel 23''' is not visible.

[0045]According to the example shown in FIG. 4 the actuators 21 are
actuated hydraulically and it is provided that both the hydraulic
actuators operating on a relative pair of forks 19 are controlled by a
common pump exclusively dedicated to them.

[0046]According to the details schematically shown in figure 6, the system
made up by the actuators 21 connected to the forks 19 belonging to the
external pair 19''', is supplied by a pump 26 exclusively dedicated to
it.

[0047]The pair of internal 19' and intermediate 19'' forks, that is the
actuators 21 connected to the respective forks 19, are alternatively
supplied by the same shared pump 27. The electronic control of the
vehicle determines the use of the shared pump 27 by a system compared to
another through electric valves 28 arranged on the circuit of each
system. In this manner, when performing the position adjustment
operations of the forks 19, at a first step the external 19''' and
intermediate 19'' pair of forks are thus positioned due to the
simultaneous intervention of their respective pumps 26 and 27. At the end
of the travel of the intermediate forks 19'', the shared pump 27 which
controlled them can subsequently serve the pair of internal forks 19',
blocked up to that point, while the external forks 19''', served by the
special pump 26, continue their opening until the desired positioned has
been attained.

[0048]According to a preferred embodiment, shown in the chart of FIG. 6,
the special pump 26 which serves the pair of external forks 19'''can be
shared with other systems, such as the tilting plate 17 hydraulic device,
used when the horizontal position of the forks 19 has already been
adjusted. In FIG. 6 this further system is indicated by a dashed line due
to the fact that it is not controlled by the actuators 21 for the
adjustment of the relative position between the forks.

[0049]Lastly, another pump 29, also indicated by a dashed line, is meant
for vertical lifting of the post structure 14.

[0050]The hydraulic operation of the circuit shown schematically is of the
known type and not described further in details. The pumps, of the
gearing type, are mounted in series and run by a motor 37.

[0051]With reference to the details shown in FIG. 3, and in particular to
the connections between the elements composing the lifting group 13, the
lifting movement of the clamp group 18 is determined.

[0052]The support structure 14 shown is composed of two parallel vertical
hydraulic actuators 30, in which a fixed part 31 has, on the side facing
the symmetry plane 22, a "double T" shaped vertical guide 33 and a
moveable part 32, vertically extendable beyond the relative fixed portion
31, is connected at an upper end to a "double T" shaped vertical guide
33'.

[0054]Thus due to its rotating bearings, the lift truck 15 can move
vertically with respect to the post structure 14 and such motion is
transmitted, according to a preferred embodiment shown in FIG. 3, by
pulleys 35 and chains 36 which are constrained at one end to the lift
truck 15 and at the other end to the moveable portions 32 of the post
structure 14.

[0055]Thus, lifting the moveable portions 32, they also draw the lift
truck 15 vertically. Lastly, the rotating coupling means 16 of the
tilting plate 17 with respect to the lift truck 15, as shown in FIG. 3,
are two horizontal-axis hinges which connect, at the upper part, plate 17
to the lift truck 15.

[0056]In such manner, a tilting rotation of the plate 17 is allowed for
enhanced stability of the pallets against the forks 19 when moving them.
According to the invention, in order to enhance safety and accuracy when
using the vehicle 10, the forks 19 comprise optical sensors 40, mounted
at their ends in special seats 41, for optical scanning of the space in
front of the forks 19 themselves.

[0057]For example, these optical sensors 40 can be optical sensors of the
photocell type.

[0058]With the same objective, that is enhancing safety and accuracy of
the automatic guided vehicle 10 during use, according to the invention
other sensors, not shown, are also provided to signal the stop of the
horizontal movement of the forks 19. For example these further sensors
can be devices of the inductance or detector magnetic type.

[0059]The main aspect of the invention, as indicated beforehand, is the
presence of a pair of racks 24', 24'' and 24''' coupled with each pair of
forks 19', 19'' and 19''.

[0060]Such coupling can be of various type and, as a matter of fact, as
shown in FIG. 4, the racks 24 can be directly connected to the relative
forks 19, otherwise they can be connected to an end of the actuator 21 at
the point where it is connected to the relative fork 19.

[0061]The operation of the automatic guided vehicle with an improved
multiple-pallet lifting group subject of the present invention is very
easy to understand.

[0062]The automatic guided vehicle according to the present invention
allows, similarly to the devices known today, to move products stacked in
pallets from an initial position to another.

[0063]However in particular, the subject of the present invention has an
improved multiple-pallet lifting group for automatic guided vehicles.

[0064]As a matter of fact, given that each fork is provided with its own
special actuator, a more accurate movement of the two forks composing the
same pair is obtained.

[0065]Additionally, such fact, that is the fact that each fork is
connected to a special actuator, allows the vehicle to position all the
pairs of forks according to a non-permanent and non-preset centre
distance, but variable depending on the requirements.

[0066]For example, this allows to position the forks 19 for seizure of
one, two or three pallets, respectively nearing all the pairs of forks,
nearing the central and intermediate ones or else positioning them
distant from each other as shown in FIG. 4.

[0067]The presence of racks connected to the forks provides an ideal
synchronisation of the same. In addition, by converging the racks in a
pinion provided with a sensor, it detects the horizontal position at any
time.

[0068]The multiple-pallet clamp group 18, according to the invention,
provides possibility to keep the pallets already held on the forks apart.
As a matter of fact, in order to move two adjacent forks belonging to two
separate pairs of forks with a simultaneous movement, that is at the same
speed, the presence of pumps dedicated to each simultaneous movement and
a further mechanical constraint of the racks is required.

[0069]Lastly, the automatic guide vehicle of the present invention has
many safety devices in order to obtain proper positioning of the pallets
during picking up and laying down operations.

[0070]Furthermore, due to the various optical and/or magnetic sensors
provided for on the forks an ideal level of safety is obtained.

[0071]It has thus been observed that a vehicle with an improved
multiple-pallet lifting group for automatic guided vehicles according to
the present invention attains the objectives described beforehand.

[0072]The automatic guided vehicle with an improved multiple-pallet
lifting group of the present invention thus conceived is susceptible to
various modifications and variants, all of which fall within the same
inventive concept; furthermore all details can be replaced by other
technically equivalent elements. In practice, the material used,
alongside their dimensions, may vary depending on the technical
requirements.